4 Weeks Too Short to Show L-Carnitine Benefit

NEW YORKSupplementation with 2 g/d of L-carnitine for one month did not reduce fatigue in cancer patients in a new study published in the Journal of Clinical Oncology (2012 Sep 17).

Duffy MacKay N.D., vice president, scientific and regulatory affairs, the Council for Responsible Nutrition (CRN), said this study is just one piece in the mounting evidence of L-carnitine's effects. "It's far from concluding that carnitine doesn't work; I don't think any scientist would say that. In my opinion, the science is just getting started.

Fatigue is often a side effect of medication and treatment of cancer. MacKay said evidence is clear that  cancer patients are deficient in L-carnitine, which means they are not able to make a lot of energy from beta oxidation.

in this double-blind, placebo-controlled trial, American researchers evaluated patients with invasive malignancies and fatigue who were randomly assigned to either 2 g/d of L-carnitine oral supplementation or matching placebo.

Both the L-carnitine and placebo groups reduced their fatigue scores, based on the Brief Fatigue Inventory (BFI) by about one point (L-carntine reduction was 0.96, and placebo reduction was 1.11). There were no statistically significant differences between arms (P=0.57). Secondary outcomes, including fatigue measured by the Functional Assessment of Chronic Illness Therapy-Fatigue instrument, depression and pain, also did not show significant difference between arms.

L-carnitine also didn't reduce fatigue or other outcomes in patents who were L-carnitine-deficient at the beginning of the trial.  

MacKay noted previous human studies that showed L-carnintie had a positive effect on energy used 3 or 4 g/d, much more than the 2 g/d used in this study. "Science builds on itself," MacKay said. "We're trying to determine the optimal amount of L-carnitine to give. This is just one of many studies that should be done to explore its potential. In this four-week trial with 2 g/d, it appears there wasn't a statically significant effect. We need to do a longer study with a higher dose."

MacKay said research may one day show L-carnitine affects different types of patients in different ways. "There are so many different types of cancer and different types of treatments. We may realize L-carnitine works excellently for specific types of chemo treatment and it doesnt work so well for others." He added fatigue is a side effect of many diseases, and it's possible L- carnitine may help with other types of patients.

"It's not rock solid science yet, but we do know it's safe," MacKay added. "The good news is patients can try it, it's relatively inexpensive, it's safe, it doesnt interfere with chemo as far as we know, and if it doesn't work for their fatigue, they'll know it, and they can give it up."

And as with all supplements, we shouldn't be surprised that L-carnitne isn't a wonder cure for cancer fatigue. "While many nutritional supplements have a place integrating into people's medical treatment of serious disease, overall they are for staying healthy. We don't have anything that works for cancer fatigue. Let's put this in context, and not throw the baby out with the bath water."

L-carnitine is a popular complementary and alternative medicine supplement used to boost energy. The body can produce carnitine in the liver from fellow amino acids lysine and methionine. It is found in red meats, dairy, fish and tempeh, but many choose to supplement to increase intake. L-carnitine transports long-chain fatty acids across the inner mitochondrial membrane; the mitochondria influences energy production. The fatty acids transported by L-carnitine are broken down through a process called beta-oxidation, resulting in the production of adenosine tri-phosphate (ATP). ATP is the central energy transfer compound in cells.

A review noted treatment with L-carnitine (500 to 600 mg/day) for a period of one to four weeks in patients with cancer, but without significant anemia, increased plasma free carnitine concentrations and significantly improved fatigue and quality-of-life measures (The Oncologist May 2007 vol. 12 Supplement 1 43-51).

Studies have shown it can also reduce oxidized low-density lipoprotein (LDL) cholesterol in patients with type 2 diabetes, and it can improve sperm quality and pregnancy rates. Carnipure, a L-carnitine tartrate ingredient from Lonza, supported muscle recovery after exercise in middle-aged adults in a 2010 study.

Find more on L-carnitine and other energizing ingredients in INSIDER's recent article "Energized" by Steve Myers.